Table 2. Relative mutation rates of nucleotide i to j per site i for ex-operonic intergenic sites were calculated from singleton SNPs for the two replicatory strands.

		from A	T	C	G	Equilibrium frequency	Equilibrium AT skew
Leading	to A	-	1.79965E-04	4.37222E-04	6.39046E-04	0.2257	-0.4176 (-0.6792, -0.1522)
	T	2.34002E-04	-	1.67602E-03	1.17158E-03	0.5493
	C	6.38189E-05	4.72409E-04	-	5.32538E-05	0.1319
	G	6.59462E-04	4.49913E-05	0.00	-	0.0931
Lagging	to A	-	2.34003E-04	1.17158E-03	1.67602E-03	0.5493	0.4176 (0.6792, 0.1522)
	T	1.79965E-04	-	6.39046E-04	4.37222E-04	0.2257
	C	4.49913E-05	6.59462E-04	-	0.00	0.0931
	G	4.72409E-04	6.38189E-05	5.32538E-05	-	0.1319

Relative rates were derived from the following leading strand ex-operonic SNP counts, where XY represents a change from nucleotide X to Y: AG 31 GA 12 CG 0 GC 1 GT 22 TA 8 TC 21 TG 2 AC 3 CA 6 AT 11 CT 23. Nucleotide frequencies at compositional equilibrium were derived from the relative mutation rates. Leading and lagging equilibrium AT skews were calculated from equilibrium A and T frequencies. 95% bootstrap intervals are shown in parentheses.